What happens inside a transistor in nanometer dimensions? How can conductivity be controlled in a tiny electronic device? * And how can the efficiency of a solar panel based on nanoparticles be doubled? * Prof. Eran Rabani from the Department of Chemical Physics explains that when you reach tiny dimensions, many effects depend on quantum phenomena, and lays a scientific foundation for future technological developments
"At the end of the 19th century, there was a widespread belief among physicists that in fact all the basic laws of nature had already been discovered," says Prof. Rabani. "Then, at the beginning of the 20th century, quantum mechanics was developed, which opened up a new world for them: the world of the smallest scales - molecules, atoms, electrons, etc. Quantum mechanics revived physics, and some of the greatest scientists of the 20th century were involved in it. Today, when we deal with the nanometer world, we understand that when we reach the tiny dimensions, many effects depend on quantum phenomena. Modern technology, which strives to minimize electronic components more and more, will at some point have to deal with the quantum issue. In my group we try to accurately describe the quantum phenomena and deal with their effect on nanometer devices."
Below are several examples from Prof. Rabani's research in the field of nanoscience:
Molecular transistor
What, for example, happens in a transistor - a basic component of every electronic device - when it reaches the size of a single molecule? How does the electron flow through the molecule? To this end, it is important to study and understand the conductivity properties of materials at the nanometer level, and the problem is especially complex because it is a current: that is, a system that is not in equilibrium. To solve problems of this type, Prof. Rabani developed an innovative computational method, based on 'path integrals' - an approach developed by the father of nanotechnology, Richard Peyman. Prof. Rabani's groundbreaking approach makes it possible to accurately predict the conductivity of the material on the nanometer scale.
Enrichments in the nanometer dimension
All the electronic devices we know today are based on semi-conductors (such as silicon), which contain additions (isolations) of materials that change the conductivity. Through these connections, the device developers manage to optimally control the electronic properties of the materials, and adapt to different uses. But what happens to the semi-conductors and the insulating materials on the nanometer scale? "For many years, researchers have tried to inject impurities into nanoparticles, but without success. Without alloys, the possibility of using nanometer semiconductors, and using them to produce tiny devices, is very limited," says Prof. Ravani.
Prof. Rabani's research group, in collaboration with a group from the Hebrew University, found a solution to the complicated problem. The researchers from Tel Aviv University developed a theoretical model that explains the electronic properties of electrodes trapped inside a nanometer semiconductor, while their colleagues in Jerusalem actually carried out the innovative electrodeposition process. The new developments enable optimal control of the electronic and optical properties of nanometer semiconductors, as a basis for a wide range of applied developments in the future.
double the efficiency
According to Prof. Rabani, "many solar cells work according to the following principle: when the material absorbs the sunlight, the electrons move to an excited state. Each photon (particle of light) absorbed excites one electron, and the excited electron leaves behind a hole. Separation between the electron and the hole creates an electric charge, and the electrodes connected to the cell collect the charges. This is how an electric current is created." A solar cell operating in this way is able to utilize up to 31% of the solar energy it receives, and this is according to a theory that was already proven in the 60s. The problem is that the cost of producing such cells is very high compared to the benefits that can be derived from them. That's why scientists all over the world are looking for a way to increase the utilization on the one hand, and reduce costs, on the other hand.
"Many researchers sought to increase the utilization of cells using a method known as 'charge doubling'," explains Prof. Ravani. "The meaning is that every photon absorbed by the material will create two charge carriers instead of one. According to the theory, the utilization of such a cell can approach 50%. We investigated the process of doubling the charge in solar panels based on nanoparticles, and we came to interesting conclusions." On the one hand, the researchers proved that the method is ineffective in panels based on conventional nanotechnology, but later they showed how, by adding certain physical elements, it will be possible to build solar cells in which an efficient charge doubling process takes place, which will yield the desired results.
Prof. Eran Rabani is the Vice President for Research and Development at Tel Aviv University, and a faculty member in the Department of Chemical Physics at the School of Chemistry. He is considered a pioneer in the field of the theory of complex systems on the nanometer scale, and deals in a variety of areas: self-organization of nanoparticles, structural and electronic properties of nanoparticles, energy and charge transfer on the nanometer scale, molecular conductivity, and many-body quantum dynamics. Prof. Rabani is active in European and American scientific organizations, and was a member of scientific forums of the Israeli National Academy of Sciences, and a visiting scientist at leading universities in the world, including Harvard, Columbia, Berkeley and Ecole Normale in Paris. His many studies have been published in the most important scientific journals, and he has won many scholarships and awards, including the Chlor scholarship, the Alon scholarship, the Rothschild Foundation and the Fulbright Foundation scholarships, the Miller Center Award in Berkeley, the Yad Hanadiv Bruno Award, the Israel Chemical Society Award, the Friedenberg Award, the Bergman Award , Patai Award and Alving Award.
7 תגובות
sparrow
It's not going to stop, it's going to stop. The allocations for the LHC will perhaps be the last large allocations for this field (in the United States they refused to build a similar large accelerator on the grounds that there would be no budget left for physics researchers).
In the last decades, the schools of theoretical physics are fading away. Mostly older researchers remained there.
The decadence of theoretical physics institutions is an old matter.
Here is an old joke published about physicists about 40 years ago.
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A man in tattered clothes sits on a bench in a public park and says:
I graduated with a bachelor's degree in theoretical physics, I was looking for a job, I searched and searched and searched, I found nothing.
They told me: continue physics for a master's degree. I graduated with a master's degree. I looked for a job, I looked, I looked, I didn't find it. They told me: go and continue physics for a PhD. I finished a third degree in physics, I was looking for a job, I was looking, I was looking, I was looking and I couldn't find it. Tell me, what should I do now?
Young people hardly go to study theoretical physics, because they know that they will not be able to make a living from theoretical physics outside of academic institutions. But the academic institutions do not have many budgets for new positions in this field. Instead, the young people go en masse to study computer science, computer engineering, electronics, communications, aeronautics, space engineering, composite materials (like Professor Rabani, the subject of the article).
The standard model has nothing on the horizon that can materialize into a practical product, I bet even in a hundred years the situation will not improve. This is different from relativity, quantum and nuclear physics which were on a practical track within twenty-thirty years from the beginning of the theoretical research.
If anything comes out of the hadron accelerator, it will not be from the understanding of theoretical physics (at the level of pretentious models), but from the identification of *spot* physical phenomena (which are not proven theoretically but are discovered through trial and error).
heat
WWW is not a product of physics. It is a distinct product of computer science that has been used in many places for quite a few years. It. Nor is it a scientific concept at the highest level. The fact that the final polishing was in the middle is irrelevant, it could have been polished in ten more computer science academies around the world.
SAFKAN, invested lots and lots of money in the LHC's crazy physics. Lots!!!
And I don't think it's going to stop so soon, the investment in theoretical physics. To date, every significant advance in theoretical physics has produced many practical applications later, even if they were not obvious in the first years after that advance.
The skeptic is pragmatic; we in the country do not have the money to throw away on such accelerators.
And we have to settle for things whose applicability is close.
On the other hand, the accelerator can reveal to us new physics that was not foreseen.
But something has already come out of the accelerator: the WWW was invented in Sarn and is used today
the whole world
Luckily, there are people who deal with real physics, and there are those like commenter 'the skeptic' who deal with nonsense.
And fortunately for us such skeptics will not engage in real physics.
At last, real physics and not phony physics (big bang, Higgs particle) that has no real empirical basis.
Flamboyant physics will not survive, because it is based on meager budgets that no one will pay for a long time. No one pays for lofty promises of breakthroughs that are unlikely to ever materialize.
Without alloys, the possibility of using nanometer semiconductors, and using them to produce tiny devices, is very limited," says Prof. Ravani.
You won't hear about him on Channel 2 or Channel 10.